It is a scenario that has become all too familiar in recent years: an
exotic microbe, aided by human travel and commerce, erupts in a new setting.
In 1999, it was the West Nile virus. Earlier this year, severe acute respiratory
syndrome (SARS) exploded on the world's stage. And last month, the first cases
of monkeypox, a viral disease related to smallpox—but less deadly and
less infectious—appeared in the Western hemisphere (see "From the Centers
for Disease Control and Prevention" [CDC] 0 on page 30 in the printed journal).